title: p21-activated kinase 3 (PAK3) is an AP-1 regulated gene contributing to actin organisation and migration of transformed fibroblasts.
abstract: Activating Protein 1 (AP-1) plays a vital role in cell proliferation, differentiation and apoptosis. While de-regulation of AP-1 has been linked to many cancers, little is known regarding its downstream transcriptional targets that associate with cellular transformation. Previous studies identified PAK3, a serine/threonine kinase, as a potential AP-1 target gene. PAK3 has been implicated in a variety of pathological disorders and over-expression of other PAK-family members has been linked to cancer. In this study, we investigate AP-1 regulation of PAK3 expression and the role of PAK3 in cJun/AP-1-associated cellular transformation. Our results showed elevated PAK3 expression at both the mRNA and protein level in cJun-over-expressing Rat1a fibroblasts, as well as in transformed human fibroblasts. Elevated PAK3 expression in cJun/AP-1 over-expressing cells associated with a significant increase in PAK3 promoter activation. This increased promoter activity was lost when a single putative Jun binding site, which can bind AP-1 directly both in vitro and in vivo, was mutated. Further, inhibition of PAK3 using siRNA showed a regression in the cell morphology, migratory potential and actin organisation associated with AP-1 transformed cells. Our study is a first to describe a role for AP-1 in regulating PAK3 expression and suggest that PAK3 is an AP-1 target required for actin organization and migration observed in transformed cells.
authors.affiliation: Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Institute of Infectious Disease and Molecular Medicine, Cape Town, South Africa.
authors.forename: Nina
authors.initials: N
authors.lastname: Holderness Parker
authors.forename: Howard
authors.initials: H
authors.lastname: Donninger
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Birrer
authors.forename: Virna D
authors.initials: VD
authors.lastname: Leaner
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D002461:Cell Line, Transformed; D002465:Cell Movement / Q000235:genetics / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000235:genetics / Q000502:physiology; D004318:Doxycycline / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008856:Microscopy, Fluorescence; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D018808:Transcription Factor AP-1; D054462:p21-Activated Kinases; D004318:Doxycycline